Mobile electronic devices that are capable of music or video playback have become very popular. Such devices include relatively small special purpose devices designed only for music or video playback via earphones or headphones as well as other, typically mobile devices such as notepads, notebooks or laptops, for example. These devices, irrespective of their size or provision of built-in speaker systems are referred to herein as media players. Media players are often used also in combination with external speaker systems. As many small size media players have been developed that include large amounts of memory capable of storing lots of music, videos and/or games, users have come to use media players as a store for large media libraries. It is therefore convenient to use such a media player as a source of media data not only by itself but also in multiple other use contexts, for example, to interconnect the media player with other devices such as TVs, Hi-Fi systems, other media players or for consumption or sharing the stored media data.
Many media players allow their media to be provided via wired and/or wireless connections for reproduction of better sound quality on external speaker systems, for example. Cable, cradle, adapter or converter connections, however, require additional components and space, incur extra cost, and as such are inconvenient, in many use contexts. They can deprive media players of their mobility aspects and can disadvantageously affect the user experience. Choosing compatible cable connection with compatible plugs from the large variety of plug connectors used today, however, bears risks for connector incompatibilities, nuisance and frustration of users, just to name a few.
A particular use context for a media player often deemed useful is the combination with a vehicle audio system. Some vehicle audio systems provide interconnect systems for connecting external devices via a plug-in type audio jack or Bluetooth™, for example. Large numbers of vehicle audio systems, however, do not provide a plug-in audio jack or Bluetooth™. Vehicle audio systems including a cassette player can be used in combination with cassette converter devices that can convert audio input signals from a media player and provide the audio to the vehicle audio system via the cassette deck. Although they have been available for many years, cassette converter devices suffer from unreliable operation, are bulky, fragile, and rely on typically no longer used technology. Furthermore, the number of vehicle audio systems providing a cassette deck is diminishing.
Ever since broadcast activities within licensed spectra has been legalized and regulated for restricted uses in certain jurisdictions, short-range radio transmitter devices have been made available that can transmit signals to a vehicle audio system via radio signals. Depending on the jurisdiction, transmissions from such radio transmitters may be limited in power or entirely prohibited at frequencies that are used by a licensed broadcaster, for example.
Typical short-range radio transmitter devices are either external to or integrated in a media player. They broadcast low-power radio signals and typically employ frequency modulation (FM) for better sound quality rather than amplitude modulation (AM). Radio transmitters used today are typically referred to as FM transmitters and many of them simply transmit on a fixed frequency or frequency that can be manually set by a user. As such, playing music through a car radio requires manually setting the corresponding transmission frequency of the radio transmitter and the radio receiver of the vehicle audio system. The amount of attention required by a user for this purposes is typically considered inconvenient. Some jurisdictions consider this a safety hazard and prohibit interaction of a driver with such devices.
More recently, mobile radio transmitters have been developed that aim at providing improved comfort for a user by automatically, at least partially, assisting the setup and maintenance of an operative interconnection with a vehicle audio system. Such transmitters can also reduce the amount of interference between radio signals generated by a radio transmitter and radio signals from other sources. Solutions aim at reducing the amount of intervention required by a user to avoid interference by automating various parts of the frequency selection so the user does not have to perform a manual search for free frequencies before setting a frequency for a transmission in order to avoid signal interference and achieve a high quality transmission, for example. This is particularly relevant when initializing a radio transmission or when interference conditions change due to roaming of the radio transmitter during an active radio transmission while driving, for example. For this purpose, some FM transmitters employ an “Alternative Frequency” function (AF) of the Radio Data System (RDS) or, in North America typically referred to as the Radio Broadcast Data System (RBDS), herein collectively referred to as RDS. The AF function enables a suitably configured radio receiver to follow a broadcast signal by switching to an alternative frequency depending on the signal quality. For this purpose, the broadcast signal must include information about the alternative frequencies. RDS/RDBS can encode such information in a side-band of a FM signal. U.S. Patent Application Publication Nos. 2010/0285732 and 2008/0200125 provide examples of AF-based FM transmitters.
Therefore there is a need for a solution that overcomes at least one of the deficiencies in the art.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present technology. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present technology.